Gaseous chemical sterilants, such as ethylene oxide, are widely used for sterilizing various plastic, fabric and metal articles in sterilizing chambers. However, the dumping of these sterilants into the environment from sterilizers has been a problem for years. The sterilant may be blown toward inhabited areas resulting in persons being exposed to toxic chemicals. Some sterilants, such as ethylene oxide, can be hydrolyzed into a safer usable byproduct such as ethylene glycol. Systems are available to scrub ethylene oxide from a sterilizer discharge effluent and convert it to ethylene glycol. These systems, however, use sulfuric acid as a catalyst for hydrolysis. This technology has several disadvantages.
Sulfuric acid solutions at the required concentration for hydrolysis are hazardous to handle. In some systems the acid solution is pumped into spray nozzles at relatively high pressures and a piping failure can result in injury to personnel. In other systems the sterilant is bubbled through the acid in plastic tanks. At high flow rates the pressure can rupture the tanks. A leak in the holding tanks due to high pressure or mechanical failure can be hazardous to clean up and can damage other equipment.
Periodically, the acid scrubber liquid has to be changed as the efficiency of the system decreases. The acid solution has to be neutralized for waste disposal, usually with caustic sodium hydroxide. This introduces a further hazard. In addition, the glycol to be collected for reuse is contaminated with sodium sulfate.
The efficiency of acid scrubber systems changes with the temperature of the acid solution and the concentration of ethylene glycol which forms in the solution. The capture efficiency of the systems decreases as the ethylene glycol content or the temperature of the solution increases. If the temperature decreases, however, the rate of hydrolysis decreases. Heating and cooling of the acid solution for a more controlled capture efficiency and subsequent hydrolysis are difficult and costly.